When a cylindrical body such as an injection-molding nozzle must be heated, it is standard to use a sleeve heater that is slipped over the body and that can be electrically energized to heat the body. The heater typically is formed as a metal sleeve in which is fitted a coil of a resistive-heater element. The inside diameter of the heater is equal to or slightly greater than the outside diameter of the body to be heated.
Such a heater is normally mounted on the body simply by slipping it over the body. When the body subsequently heats up and swells, the heater is solidly locked in place. This means that prior to installation and, in fact, whenever the heater is not activated to swell the body, the two parts can easily slip apart.